The present invention relates to a method for using an apparatus for the magnetic treatment of fluids through the application of magnetic field to the fluid flowing through conduits.
Alkaline-developing photoresists are used for patterning, for example, chemical-milling and the production of printed wiring boards. As foaming during production is detrimental to the production of printed wiring boards, measures have conventionally been taken to suppress foaming through the addition of antifoaming agents. The ingredients of certain antifoaming agents, such as polyoxyalkylene ethers, glycerol monostearate, polyoxyethylene sorbitan monostearate, and coconut alcohol, are themselves contaminants in developers and the products of these printed wiring boards.
On the other hand, some ingredients of photoresists, such as polymers having a structure unit of styrenes, methyl methacrylate, ethyl acrylate, and methacrylic acid, are separated and deposited on the wall of conduits. The deposits are also contaminants in developers and the products. In order to remove the separated materials described above, 3% aqueous hydrochloric-acid solution and commercial cleaning solution; some cleaning solution containing caustic soda, sodium acetate, butyldiglycol, or surfactants; and those including hydrochloric acid or hydroxycarboxylic acid, as have conventionally been used. However, these methods involve the high costs of chemical cleansing and waste treatment, and are may not be sufficiently effective, depending on the photoresist ingredients.
In this technological environment, a magnetic water-treatment apparatus is publicly known. As the apparatus separates the association of clustered water molecules in order to reactivate them, it may also be utilized to perform defoaming in the development step described above if it functions as expected. However, as the fluid to be treated is exposed to magnetic flux generated between a pair of magnets positioned on opposite ends of a flow of water in the case of the water-treatment apparatus described above, the pair of magnets must be positioned so as to face each other. Therefore, a strong magnetic field also exists in regions other than the area under examination, resulting in the problems of a low efficiency in magnetic-field utilization and a significant loss in magnetic force. In addition, utilization of a water-treatment apparatus such as that described above, comprising a uniform magnetic field only, cannot be expected to have a significant effect.
U.S. Pat. No. 5,074,998 is an exemplary invention intended to prevent the deposition of scale inside conduits. The invention has a constitution in which solenoid-type electric coils are positioned alongside and outside or inside the conduit, a magnetic field, generated by charging the electric coils, is applied to the fluid in the conduit. Control of the strength of this magnetic field is also described in the invention. This is done by adjusting the amplifying-signal electric current of the coil to the characteristic frequency of the scale-forming substance. The fluid is exposed to a magnetic field only once while it flows through a conduit utilizing an apparatus of the invention described above.
The present invention was developed in view of the above-mentioned points, and its object is to enable magnetic-force-based kinetic energy to affect fluids flowing through conduits.
Another object of the present invention is to facilitate the removal of contaminants such as scale-forming substances existing in the fluid, by changing the coarseness (structural coarseness) of the contaminants, and to change the magnetic-force-based kinetic energy acting on the fluid in order to improve the characteristics of the fluid.
Another object of the present invention is to solve the problem of contamination of the developer and the developed products by controlling and removing foams that are detrimental to the development process without using conventional antifoaming agents, and to effectively remove insoluble substances in the development process that could not be removed by conventional methods.
Another object of the present invention is to enable stable product control in chemical milling and the production of printed wiring boards.
Another object of the present invention is to prevent so called scale that is deposited on the wall of conduits, etc. of photoresist developers such as in the development process, making it easier to clean the alkaline developer.
These and other objects have been attained by using magnetic units in which the ends of each of the yokes are arranged alternately at the N and S poles, and the other ends of said yokes being arranged so as to face each other, in order to form magnetic circuits in which magnetic flux can circulate, resulting in the positioning of the magnetic treatment part of fluids between said other ends of said yokes, with a plurality of said magnetic units being arranged such that the directions of magnetic flux generated at said parts for magnetic treatment change along the flow path of said fluids.
Thus, the present invention is characterized by the inverse application of a magnetic field to a fluid. The inverse application of a magnetic field in the present invention means switching the polarity of magnetic fields in certain regions. As a result, for example, the magnetic flux may point downward in a certain region, while it points upward in adjacent regions. Therefore, when a fluid such as developing solution passes through regions with different magnetic-flux directions, as described above, it is affected by changes in kinetic energy due to the 180-degree changes in the magnetic flux resulting from the polarity change in the magnetic fields. A magnetic field with magnetic flux having alternating directions will be referred to as an alternating magnetic field in the present invention. To form the 180 degree changes in the magnetic flux, it is desirable to insert non-magnetic spacer between adjacent magnetic units to generate an alternative magnetic field stably.
Although the present invention is common to the conventional magnet-type water-treatment apparatus, it also utilizes the effect of the changes in kinetic energy accompanying the inversion of magnetic polarity. Thus, according to the present invention, both the changing magnetic energy and kinetic energy may be applied to water molecules and the like in the developing solution.
The magnetic circuit described above contains blocks of magnetic material polarized to the N pole and the S pole on its largest face, and a yoke with its end magnetically attracted to said polarized surface and other parts arranged so as to surround the flow of the developing solution, and this magnetic circuit configured so that the magnetic flux circulates. The strength of the magnetic flux per unit area is maximized by polarizing the N pole and the S pole in the largest area of the blocks of strongly magnetized magnetic material (permanent magnet), enabling efficient magnetization of fluids or of other objects such as solvents, solutes, dispersion, etc.
The present invention is also applicable to the removing of scale containing components such as polymeric polymerizing binders, polymerizable substances, and additives deposited on the flow paths and the tank of developing solutions in the developer, wherein it is desirable to use as cleaning liquid aqueous solutions containing one or more than one ingredient of the components polyearboxylic acid, malic acid, EDTA, and saponin, and to remove the insoluble deposits by exposing said aqueous solution to an alternating magnetic field and then flowing it onto the flow paths and into the developing-solution tank.
The scale formed by deposition due to the use of developers mainly contain one or more than one ingredient of the following: polymeric binders, polymerizable substances, and additives. The polymeric binder used is typically an acrylic ester copolymer, styrene-methyl methacrylate copolymer, or ethyl methacrylate- methacrylic acid copolymer. The polymerizable substances used include photo-cross-linking monomers such as ethylene diacrylate, diethyleneglycol diacrylate, trimethylolpropane triacrylate, bismethacrylate of polyethyleneglycol, ethoxylated alcohol, or phenol (such as 2,2xe2x80x2-bis [4-(methacrylxydiethoxy) phenyl]propane), and methylenebismethacrylamide. These substances also contain polymerization initiators as additives. Examples of them are 1-chloroanthraquinone, 2,2xe2x80x2-methylenebis (4-ethyl-6-tert-butylphenol), 4,4xe2x80x2-bis (dimethylamino) benzophenone, and benzotriazole.
Said specific cleaning liquid is used to remove scale containing such ingredients. It is necessary to subject this cleaning liquid to magnetic treatment by exposing it to the alternating magnetic field. Among the ingredients of said cleaning liquid, polycarboxylic acid contains one or more than one ingredient of the following: malic acid, citric acid, glutaric acid, adipic acid, succinic acid, oxalic acid, tartaric acid, phthalic acid, fumaric acid, and malonic acid. In addition to polyearboxylic acids, ethylenediaminetetraacetic acid (2 sodium salt, EDTA) may also be used. These are used as aqueous solutions. Among said acids, an aqueous solution of polycarboxylic acid such as malic acid and EDTA is desirable.
In the case of malic acid and EDTA, for example, the EDTA content is desirably 3-7 wt parts. A cleaning liquid within said range of EDTA content can achieve its purpose through the synergistic effect of the magnetic treatment to be described below. On the other hand, cleaning liquid outside of this range of EDTA content cannot fully achieve its purpose even with magnetic treatment.
When 5-15 wt parts of cations such as silicon, barium, and magnesium are included in the scale, a mixed aqueous solution of one or more than one ingredient from among tetramethylammonium hydroxide, triethanolamine, and monoethanolamine, and either sodium hydroxide or potassium hydroxide, are used as the cleaning liquid. Through the use of this mixed aqueous solution following magnetic treatment, effective cleaning can be performed in a single-liquid process.
The magnetic treatment described above is conducted by exposing the cleaning liquid comprised of said aqueous solution to an alternating magnetic field, or by applying the alternating magnetic field to the cleaning liquid. As described above, the alternating magnetic field contains multiple magnetic fields formed fully across the flow path of fluids such as cleaning liquids, developing solution, and the like, with the direction of the magnetic flux of adjacent magnetic fields being opposite and in alternation. The direction of said magnetic flux will cross the flow of fluids at nearly right angles. Though the alternating magnetic field is applied at the top of the highest stream and any required positions downstream from that point, if the fluid is circulable it may be applied anywhere within the circulation, upstream or downstream.
It is desirable to form magnetic fields that fully cross the flow path of the fluid by using a magnetic treatment apparatus with which yokes are polarized into N and S poles by positioning the ends of the magnetic yokes at the N-pole side and the S-pole side of a magnetic body, and in which the flow path is located between the other ends of the yokes. See FIG. 2. The change in kinetic energy accompanying the inversion of magnetic polarity in such magnetic fields can produce highly active water by disrupting the association of water molecules that may have occurred in the flowing water, as if a vibration had been applied.
According to the present invention, substances that cause foaming are dispersed through the application of an alternating magnetic field to the aqueous solution that flows through a developer, so that scale may be prevented from developing even when the apparatus is not being cleaned. Thus, cleaning efficiency is significantly improved through the application of an alternating magnetic field together with cleaning liquid, while the cleaning process may be significantly simplified through the application of an alternating magnetic field to the developing solution during the developing process, due to the reduction in the amount of scale deposition.
Water can be activated by the magnetic treatment exposing cleaning liquid to an alternating magnetic field. At the same time, nucleophilic/electrophilic and positive/negative bipolar water-soluble substances can be produced within the molecules of the components of the aqueous solution, and insoluble monomers are added to the bipolar water-soluble substances through reactions to turn them into water-soluble scale. The mechanism in the present invention may be best explained in this manner.